Device for stabilizing distance between tool secured on support of machine,for example cutter of gas-cutting machine,and surface of blank

ABSTRACT

A device for stabilizing the distance between a tool secured on the support of a machine, for example, the cutter of a gascutting machine, and the surface of a blank, in which a detector determining the position of the tool has at least two pairs of indicators following the distance between the blank surface and a mark made on the surface of the tool or support of the machine and corresponding to each indicator, in which case the accuracy of machining the members is considerably increased.

I United States Patent I 3,595,545

[ 72] Inventors Valentin Mikhailovich Sitnichenko [56] References Cited ri a li ga tlfimh I UNITED STATES PATENTS exan i ovic amuruev, u itsa Termhkovoi, 12, kv. 24; Andrei Isakovich 33338;; 51322 ZQJ LXE Kogut, ulitsa Pionerslraya, 20, kv. 12, all of Odessa, U.S.S.R. Primary Examiner-Maynard R Wilbur [21] Appl. No. 866,987 Assistant ExaminerThomas J. Sloyan [22] Filed Oct. 16, 1969 Attorney-Waters, Roditi, Schwartz & Nissen (45] Patented July 27, 1971 [54] DEVICE FOR STABILIZING DISTANCE BETWEEN TOOL SECURED ON SUPPORT OF MACHINE, FOR EXAMPLE CUTTER 0F GAS-CUTTING MACHINE, AND SURFACE OF BFANK ABSTRACT: A device for stabilizing the distance between a 2 chimsnnwing tool secured on the support of a machine, for example, the [52] US. Cl 266/23 M, cutter of a gas-cutting machine, and the surface of a blank, in 219/125 R, 235/ 151.11 which a detector determining the position of the tool has at [51] lnt.Cl. ..B23k 7/00, least two pairs of indicators following the distance between B231: 9/12, G06f 15/46 the blank surface and a mark made on the surface of the tool [50] Field of Search ..235/61.6 H, or support of the machine and corresponding to each indica- 151.1l X; 318/20.135; 219/98, 99, 125; 266/23 tor, in which case the accuracy of machining the members is M; 148/9 considerably increased.

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PATENIED JUL27 lsn SHEET 2 OF 2 The present invention relates to devices for controlling machine tools and, more specifically, it relates to devicesfor stabilizing the distance between a tool secured on the support.

ofa machine, for example, a cutter of a gas-cutting machine, and the surfaceofa blank.

Known in a prior art are devices for stabilizing a distance between a gas cutter secured on the support of a gas-cutting machine and the surface ofa blank, in which a detector determining the position of the cutter relative to the blank surface indicates the distance betweenthe surface of the blank and a mark located at some distance from the cutter axis on the surface of the cutter or support of the machine, said detector being coupled with the support drive.

In these devices, the detector determining the position of the cutter relative to the blank surface comprises only one indicator responding to a change in the distance between the blank surface and the mark. Due to a displacement of the mark from the cutter axis askew the blank surface relative to a plane perpendicular to this axis there occurs a metering error. The latter also appears in the case of an uneven surface of the blank (for example, deposits of slag, metal, etc.

An object of the present invention is to eliminate the abovementioneddisadvantages.

The principal object of the invention is to provide a device for stabilizing the distance between a tool secured on the support of a machine, in particular, the cutter of a gascutting machine, and thesurface of a blank, which device makes it possible to increase the accuracy and reliability of operation of the system for stabilizing the tool over the surface of the blank in the presence of slag and metal deposits on this surface and also in the'case in which the blank surface is not parallel to the plane perpendicular to the tool axis.

This object is attained by means of a device for stabilizing the distance between a tool secured on the support of a machine, in particular, the cutter of a gas-cutting machine, and the surface of a blank, in which the detector of the position of the tool relative to the blank surface determines the distance between the blank surface and a mark disposed on the surface of the tool or support of the machine at a certain distance from the tool axis, said detector being connected with the machine drive; according to the invention, the detector of the proposed device comprises at least two pairs of indicators following the distance between the blank surface and the mark made on the surface of the tool or support of the machine and corresponding to each indicator, said marks being located approximately in a plane perpendicular to the tool axis and at both sides from the latter, and the detector is provided with logical OR circuits in a number which corresponds to that of the pairs of indicators, the inputs of said circuits being connected to the outputs of the indicators corresponding to the marks located on both sides from the tool axis, and with a logical AND circuits the inputs of which are connected with the outputs of the logical OR circuits, the output signal of the logical AND circuit controlling the drive of the machine support.

The employed indicators, for example, mechanical or inductive indicators, are preferably secured on the end face of the machine support along a circle the center of which coincides with the tool axis and at approximately equal distances therefrom, in which case the points of fixing of the indicators to the support serve as the marks.

Owing to such a construction of the proposed device the accuracy of machining the articles is increased. 7

The invention will be further described by way of example, reference being made to the appended drawings, in which:

FIG. 1 is an elevation view of a group of indicators of a detector of a position of a tool relative to the blank surface;

FIG. 2 is a schematic diagram of the proposed device; and

FIG. 3 is a graphical illustration of the metering error of the proposed device.

The device for stabilizing the distance between a tool secured on a machine support and a surface of a blank will be considered with reference to the case of stabilizing the distance between a cutter 1 (FIG. 1) secured on a support 2 of a gas-cutting machine (not shown) and the surface ofa metal sheet 3 being cut.

The proposed device comprises a detector 4 (FIG. 2) to determine the position of the cutter 1 relative to the surface of the metal sheet 3 being cut. The detector 4 is connected through a power amplifier 5 a drive 6 of the support 2 of the gas-cutting machine for moving the cutter 1 along its axis.

The detector 4 for determining the position of the cutter I relative to the surface of the metal sheet 3 being cut comprises four pairs of mechanical indicators 7-8, 9-10, 11-12 and 13-14 secured on the end face 15 (FIG. 1) of the support 2 along a circle 16 (P16. 2) at approximately equal distances from its center through which passes the axis of the cutter 1 (the circle 16 and the axis 17 of the cutter I are conventionally shown in FIG. 2). The detector 4 for determining the position of the cutter 1 has logical circuits OR 18, 19, 20, 21 the number of which corresponds to that of pairs of the indicators 7-8, 9-10, 11-12, 13-14, and the inputs of which are connected to the outputs of the corresponding pairs of the indicators 7-8, 9-10, 11-12 and 13-14, respectively, and a logical circuit 22 AND whose inputs are connected to the outputs of the logical circuits 18-21 and whose output is connected to the power amplifier 5.

The indicators 7-14 of the detector 4 determining the posidicator coincides with the end face 15 of the support 2 of the gas-cutting machine.

However, other embodiments of the invention may be proposed in which the detector 4 to determine the position of the cutter 1 relative to the surface of the metal sheet 3 being cut may comprise two pairs of indicators, three pairs, etc. These indicators may be mounted in another place but in any case they should follow the distance between the surface of the metal sheet 3 being cut and the mark corresponding to each indicator. These marks should be located on the surface of the cutter 1 or support 2 of the gas-cutting machine approximately in one plane perpendicular to the axis 17 of the cutter 1 but at both sides of this axis and at a certain distance therefrom. In this case, the inputs of the logical circuits OR should be connected to the indicators corresponding to the marks positioned on both sides from the axis 17 of the cutter The principle of operation of the proposed device consists in the following.

When the indicators 7-14 do not contact the surface of the metal sheet 3 to be cut there are no signals at their outputs, therefore, there is no signal at the input of the logical circuit AND, and the drive 6 of the support 2 moves the cutter l with the position detector 4 towards the surface of the sheet 3 along the axis 17 of the cutter 1. At the moment when the indicator, for example, indicator 7, contacts the surface of the metal sheet 3 being cut, a signal appears at the output of this indicator. Therefore, this signal also appears at the output of the logical circuit 18.

If theindicators located on any half of the circle 16 contact the surface of the metal sheet 3, the signals appear at the outputs of all logical circuits 18-21. These signals through thelogical circuit 22 are applied to the input of the power amplifier 5 whose output signal controls the drive 6 of the support 2. The latter moves the cutter 1 with the position detector 4 from the metal sheet 3 being cut along the axis 17 of the cutter 1.

If the parallelism between the surface of the sheet 3 being cut and the plane perpendicular to the axis 17 of the cutter 1 is disturbed, the position detector 4 operates as described above.

in this case, the signal at the output of the logical circuit 22 appears or disappears only at the moment of contact of any fourth indicator located on any half of the circle 16 or during the upward movement of this indicator. As a result, a group composed of any four indicators located on any half of the circle 16 is equivalent to a single indicator located at a shorter distance from the axis 17 of the cutter l (and, therefore, measuring more accurately the distance between the cutter l and the surface of the metal sheet 3 being cut) than the radius R of the circle 16 as shown in H0. 3.

Let us assume thatch is the projection of the greatest slope line, laying on the surface of the metal sheet 3 being cut, in the plane perpendicular to the axis 17 of the cutter 1. The axis of the cutter 1 is moved from a to b approaching the surface of the sheet 3.

In this case, the signal produced by the indicator 13 will appear first. After that, the signals will appear which are produced by the indicators 8, 9 and 10. If the equivalent indicator is positioned on ab, the appearance of the signals would correspondto the positioning of this equivalent indicator at points 23, 24, 25," and 26. Thus, this group of the indicators 11, 13, 8, and 10 may be replaced by an equivalent indicator positioned at point 26. The contact of the other indicators 9, 7, 14, and 12 with the surface of the sheet 3 will not take place because the drive 6 of the support 2 will lift the cutter 1 with the position detector 4.

The position of this equivalent indicator is determined by the angular position of ab within the central angle formed by the radii R of the circle 16 passing through the indicators 13 and 8.

By indicating the smaller angle between ab and one of said radii R as a, we determine the distance r (which is proportional to the metering error) between the axis 17 of the cutter l and the point 26. Due to mutual perpendicularity of the sides of said angles, the angle between the radius passing through the indicator 10 and the line connecting the indicator 10 with point 26 is also equal to a. In this case, g R

inasmuch as this expression is an equation of the circle with a radius R/2 and a center at point 27 in polar coordinates the center of which coincides with the axis 17 of the cutter 1, the geometrical place of the points of the position of the equivalent indicator on the projection ab during rotation of all indicators 7-14 about the axis 17 of the cutter 1 may be found easily by constructing circles with radii R/2 having centers at the points 2734.

value of the central angle formed by the As shown in the-drawing, the maximum value r'is obtained in case of the maximum value of the angle 01 equal to the half radii 'R passing through two adjacent indicators. 1

So at four pairs of the indicators 7-8, 9-l0, 11-12 and 13-14 Alongside with an increase of the number of pairs of the indicators the value r,,,,, rapidly decreases. in this manner, at six pairs of the indicators r,,,,,,r=Rsin(360/l2-2)=0.26R i.e., in practice the equivalent indicator will he placed under the cutter 1 within the flame zone, thus reducing the metering error, while physically the indicators are located within a safe zone at a sufficiently large distance from the cutter flame.

The proposed device provides for a higher accuracy of maintaining a prescribed distance between the gas cutter and the surface of the metal sheet being cut, the same being applied to the edge areas of the sheet.

We claim:

1. A device for stabilizing the distance between a tool secured on the support of a machine, in particular, a cutter of a gas-cutting machine and the surface of a blank, said device comprising, in combination: a detector to determine the posi tion of said tool relative to the surface of said blank; a group of marks located on the surface of said tool or said support of said machine a proximately in a plane perpendicular to the axis of said too said marks being positioned on both sides of said axis at a certain distance therefrom; said detector including at least two pairs of indicators corresponding to respective marks and following the distance between the surface of said blank and said corresponding marks; OR logical circuits in a number which corresponds to that of pairs of said indicators, the inputs of said OR logical circuits being connected to the outputs of said indicators; an AND logical circuit having inputs which are connected to the outputs of said OR logical circuits; and means for moving said support of said machine controlled by the output signal of said AND logical circuit.

2. A device as set forth in claim 1, in which said indicators of said position detector are fixed on the end face of said support of said machine along a circle, through the center of which passes the axis of said tool, said indicators being located at equal distances from said axis and the places of fixing said indicators serving as said marks. 

1. A device for stabilizing the distance between a tool secured on the support of a machine, in particular, a cutter of a gascutting machine and the surface of a blank, said device comprising, in combination: a detector to determine the position of said tool relative to the surface of said blank; a group of marks located on the surface of said tool or said support of said machine approximately in a plane perpendicular to the axis of said tool, said marks being positioned on both sides of said axis at a certain distance therefrom; said detector including at least two pairs of indicators corresponding to respective marks and following the distance between the surface of said blank and said corresponding marks; OR logical circuits in a number which corresponds to that of pairs of said indicators, the inputs of said OR logical circuits being connected to the outputs of said indicators; an AND logical circuit having inputs which are connected to the outputs of said OR logical circuits; and means for moving said support of said machine controlled by the output signal of said AND logical circuit.
 2. A device as set forth in claim 1, in which said indicators of said position detector are fixed on the end face of said support of said machine along a circle, through the center of which passes the axis of said tool, said indicators being located at equal distances from said axis and the places of fixing said indicators serving as said marks. 